Strigolactones: ecological significance and use as a target for parasitic plant control

Abstract

Parasitic weeds cause severe damage to important agricultural crops. Although some promising control methods against these parasitic plants have been developed, new strategies continue to be relevant in integrated approaches. The life cycle for root parasitic weeds is intimately associated with their host and is a suitable target for such new control strategies, particularly when directed at the early stages of the host-parasite interaction. Here, the authors focus on knowledge of the germination stimulants-strigolactones-for the root parasitic plants Striga and Orobanche spp. and discuss their biosynthetic origin, ecological significance and physiological and biochemical regulation. In addition, the existing and possible new control strategies that are based on this knowledge, and that could lead to more efficient control methods against these root parasitic weeds, are reviewed.

Ecological relevance of strigolactones in nutrient uptake and other abiotic stresses, and in plant-microbe interactions below-ground

“…Broomrapes are generally found in more temperate regions such as southern Europe, the Mediterranean area, Central Asia and the Americas, and witchweeds appear in warmer areas, mainly in Africa (Parker 2009). Although these parasites affect different hosts in different parts of the world, their lifecycles are broadly similar, starting with seed germination in response to SLs (López-Ráez et al 2009;Xie et al 2010). Upon germination, they attach to the roots of the host plant through a specialized organ called haustorium, and acquire all the nutrients and water they need to complete their lifecycle (Bouwmeester et al 2003;Estabrook and Yoder 1998).…”

“…Upon germination, they attach to the roots of the host plant through a specialized organ called haustorium, and acquire all the nutrients and water they need to complete their lifecycle (Bouwmeester et al 2003;Estabrook and Yoder 1998). After emergence, they produce a large amount of seeds, increasing the seed bank in the soil, which is one of the major problems in the control of these parasites (López-Ráez et al 2009;Xie et al 2010). In addition, most of their life cycle occurs below-ground, making diagnosis difficult such that the parasites usually have already inflicted irreversible damage.…”

“…Since these parasites exert the greatest damage prior to their emergence, such strategies should mainly focus on the initial steps of infection, particularly seed germination triggered by SLs and attachment (Fernández-Aparicio et al 2011;López-Ráez et al 2009;Yoder and Scholes 2010). Breeding for cultivars with reduced SL production and/or exudation could be a suitable strategy to combat these pests.…”

Destabilization of strigolactone receptor DWARF14 by binding of ligand and E3-ligase signaling effector DWARF3

“…SLs also function as signal molecules secreted into the soil to promote root colonization by arbuscular mycorrhizal fungi and to stimulate symbiosis with nitrogen-fixing bacteria [1][2][3][4][5]. The secreted SLs are also recognized and exploited as germination signals by parasitic weeds that cause devastating crop losses in developing countries [6,7].…”

Structure-activity relationship of naturally occurring strigolactones in Orobanche minor seed germination stimulation

“…6,7) Therefore, it is important to clarify the structure-activity relationships of SLs in these three different functions to develop feasible control measures for root parasitic weeds without or with little effects on AM symbiosis and/or shoot architecture. 8,9) In the present study, naturally occurring SLs, including those isolated recently in our laboratory, were examined for their germination stimulation on the seeds of a root parasitic plant, Orobanche minor Sm., and the structure-activity relationships of SLs in the stimulation of O. minor seed germination are discussed.…”